Treatment of unstable pelvic ring injury with a dual internal anterior subcutaneous fixator using spinal instrumentation called “dual INFIX”: A case report

INTRODUCTION: External fixation, various subcutaneous screw fixations, and plate fixation can be considered as fixation methods for unstable pelvic ring fractures. We describe a first case of treated unstable pelvic ring injury using a dual internal anterior subcutaneous fixator we called “dual INFIX,” comprising four screws, two subcutaneous rods, and two cross-link connectors, without posterior fixation. CASE REPORT: An 81-year-old man sustained an unstable pelvic injury (AO type B2) with fracture of the left ilium and pubis. Dual INFIX was used to stabilize the pelvic ring injury. Polyaxial screws were introduced along a path between the anterior inferior iliac spine and ipsilateral posterior superior iliac spine until the head of the screw lay immediately above the fascia. Bilateral cranial screws were connected by a rod passed subcutaneously, and caudal screws were connected by the other rod. Finally, cross-link connectors connected cranial and caudal rods on the right and left. One year after the first operation, the patient could walk without a cane and had no limitation of daily living and bony fusion was achieved. CONCLUSION: The stability of the pelvic ring of dual INFIX was sufficient to achieve bony fusion in this case. The stability of dual INFIX should be stronger than that of INFIX. Dual INFIX as with INFIX has other advantages such as ease of management compared with external fixation, and nonnecessity of strict anatomical reduction compared with various percutaneous screw fixation. Furthermore, this technique is simple and minimally invasive compared with plate fixation because it does not require open surgery. However, because the type C fracture with an unacceptable position of reduction by closed reduction has the possibility to become a symptomatic malunion, such cases should not be treated by this method. Furthermore, it is necessary for pelvic stabilization using dual INFIX that the contralateral pelvis is intact because dual INFIX stabilizes the fracture side with the other side of the pelvis. Dual INFIX can be considered as an option of fixation methods for type B-1 or 2 pelvic ring injuries.